This is the public portion of Mr. Pepin's thesis defense. His advisor is Priscilla Cushman.

An ever-increasing amount of evidence suggests that approximately one quarter of the energy in the universe is composed of some non-luminous, and hitherto unknown, "dark matter." Lower-mass dark matter has become more prominent in the past few years. The Cryogenic Dark Matter Search (CDMS) detectors can be operated in an alternative, higher-biased mode, to decrease their energy thresholds and correspondingly increase their sensitivity to low-mass WIMPs. This is the CDMS low ionization threshold experiment (CDMSlite), which has pushed the frontier at lower masses. This dissertation describes the second run of CDMSlite at Soudan: its hardware, operations, analysis, and results. The results include new WIMP mass-cross section upper limits on the spin-independent and spin-dependent WIMP-nucleon interactions. Thanks to the low background and threshold, these limits are the most sensitive in the world below WIMP masses of ~4 GeV/c^2. This also demonstrates the great promise and utility of the high-voltage operating mode in the future SuperCDMS SNOLAB experiment.